Throttle and inlet valves for 8 stroke and 4 stroke engines

ABSTRACT

An 8 stroke and 4 stroke piston engine with at least one inlet valve where there is a small volume, namely less than 10% of the swept cylinder volume, of inlet air between the seat of the throttle and the seat of the inlet valve at idling speed. The throttle can be disc or cone shaped or shaped to generally fill the volume between the closed throttle and the inlet valve seat. For higher power the throttle moves away from the inlet valve to open the inlet port. Fuel is injected into the small volume between the throttle and the inlet valve where engine heat helps vaporise the fuel without heating a large mass of the inlet air.

BACKGROUND

This invention describes an improved inlet and throttle design for piston engines.

The power output from petrol engines is usually controlled by a throttle which is some distance from the combustion chamber. There is a relatively large volume of air between the throttle and the inlet valve seat. This is unhelpful in particular conditions and can cause a high idling speed. There was a problem in Blackburn 8 Stroke and 4 Stroke cycle change or ‘Cool Charge’ engines as U.S. Pat. No. 5,598,819 and related patents. In 8 Stroke mode ‘air only’ remained in the cylinder head at the end of the ‘air only’ exhaust stroke. This volume of air was about 10% of the swept volume. If the volume in the inlet pipe between the throttle and the inlet valve seat is also 10%, then even if the throttle is nearly closed, the cylinder is nearly 20% full for the next combustion. This gave too much power and caused a high idling speed.

The present invention replaces the usual throttle valve located upstream from the inlet valve with a sliding throttle which is close to the inlet valve when the throttle is nearly closed for idling. A lower power and idling speed can then be achieved reducing the fuel needed.

DESCRIPTION

There is provided an 8 stroke and 4 stroke cycle change engine where the small volume of fresh fuel/air mixture needed for a low idling speed is controlled by a throttle, movable along or adjacent to an inlet port, with a throttle seat close to an inlet valve seat.

The throttle can be plug or disc shaped or cylindrical or any other shape which can slide in a housing or bore to close the inlet port when less engine power is needed. When more power is needed the throttle is moved away from the inlet valve, opening more of the inlet port to allow more air to enter the engine during an induction stroke. The inlet port is fully open when the throttle is moved fully away from the inlet valve providing an unobstructed inlet duct. There is preferably one such throttle per cylinder on 1, 3 or 5 cylinder or other multi-cylinder engines.

A preferred throttle is a plug type of throttle, usually disc shaped which can slide towards and away from the inlet valve within a bore which is set at an angle to the axis of the inlet port in such a way that the plug can open and close the inlet port itself. A control is attached to the plug throttle and leads out of the inlet port area via a seal. The control can be a rod attached directly or indirectly to the accelerator pedal. Alternatively an electric servo can operate the plug throttle outside or inside the inlet port area. The control can be mechanical, electrical or other means influenced by the accelerator pedal position, a microprocessor, computer, driver preferences, oil, air or water temperature and atmospheric conditions.

The surface of the plug throttle itself can be a plain disc. Alternatively it can be cone shaped which has the effect of reducing the volume of air between the throttle seat and the inlet valve seat. In some circumstances it may be advantageous to further reduce the volume between inlet and throttle valves. Then the head of the plug throttle is shaped to partly fill the space around the inlet valve stem. Clearance allows the throttle to open or close as needed. In this case the volume between the throttle and inlet valve seat is less than 5% of the swept cylinder volume.

As already indicated a small volume is desirable between the throttle and inlet valve seats to provide a low idling speed. However, this low volume also allows the throttle to be more open for a given engine speed or power. The control is thus less sensitive and less affected by wear, expansion, contraction or atmospheric variations.

When the throttle is slightly open for low power and the inlet valve is closed, the very small volume between the throttle and inlet valve seats fills quickly. The pressure in this space is then close to atmospheric when the inlet valve opens for the next induction. Little if any of the cylinder contents is then sucked back into the inlet when the inlet valve opens. This contrasts with the volume of hot exhaust gas which is sucked into the larger inlet port space of a conventional engine by the vacuum which remains relatively constant at low or idling speed. The temperature of the fresh air intake is reduced by this invention which helps fuel efficiency.

A preferred location for the fuel injector is between the throttle and inlet valve seats when the heat from the cylinder head vaporises the fuel without causing a large temperature rise for the bulk of the inlet air which would reduce the fuel efficiency of the engine. Inlet air turbulence in the space between the throttle and inlet valve seats helps mix the fuel and air prior to the pre-mixture being drawn into the engine cylinder. Better fuel/air mixing gives more complete and faster combustion.

The inlet valve itself is operated by a cam either directly or via a rocker or link. The cam follower is convex or radiused and the cam form is concave at the point where the inlet valve starts to open and where it ends closing to minimise impact, noise and wear. The cam opens and closes the inlet valve with approximately 60 degrees of cam rotation.

A piston engine can have one or more inlet valves in a cylinder generally as described above. Preferably each cylinder has one inlet valve as described above and a second inlet valve with no throttle but provision to switch its separate fuel injector on or off for an induction as needed for a particular power output.

The plug type throttle is mainly intended for ‘8 Stroke’ or ‘Cool Charge’ engines but may also be applied to 4 stroke or 2 stroke engines. With all inlet valve alternatives at least one exhaust valve and other usual components are fitted (not shown).

The fuel injector can also be located in the outer part of the inlet port or directly in the combustion chamber.

DETAILED DESCRIPTION

A preferred embodiment of the invention will now be described with reference to FIG. 1/1.

Piston 1 operates in cylinder 2 which is closed by cylinder head 3. Inlet valve 4 is operated by cam 5 via cam follower 6. Inlet port 7 leads on to a small chamber 8 which is nearly sealed by throttle 9 at idling speed. Throttle 9 can move in bore 10 away from inlet valve 4 to open the throttle and inlet port 7 to allow more air to enter the engine during an induction stroke. Attached to throttle 9 is control rod 11 which is connected directly or indirectly to the accelerator pedal (not shown). Fuel injector 12 injects fuel into the space between the throttle and inlet valve seat. Cam follower 6 has a convex form while cam 5 has a concave shape 13 to start opening and finish closing inlet valve 4. A cone shaped end 14 is shown on throttle 9 to reduce-the volume in chamber 8. Similarly the inner end of throttle 9 can be shaped to substantially fill chamber 8 for idling speeds but maintaining clearance to allow easy opening and closing of the throttle (not shown). 

1. I claim an internal combustion engine where there is a small volume of inlet air, namely less than 10% of the swept cylinder volume, between the seat of the throttle and the seat of an inlet valve at idling speed.
 2. I claim a cycle change engine with ‘air only’ inductions between 4 stroke cycles with fuel/air inductions where there is a small volume of inlet air, namely less than 10% of the swept cylinder volume, between the seat of the throttle and the seat of an inlet valve at idling speed.:
 3. I claim an 8 stroke and 4 stroke cycle change engine with ‘air only’ inductions between 4 stroke cycles with fuel/air inductions where there is a small volume of inlet air, namely less than 10% of the swept cylinder volume, between the seat of the throttle and the seat of an inlet valve at idling speed.
 4. A claim as claimed in claim 1 where a throttle in an inlet port moves towards the inlet valve seat to reduce the air entering the engine cylinder when less than full power is needed and moves away from the inlet valve seat to open the inlet port for higher power.
 5. A claim as claimed in claim 1 where the throttle is disc or cone shaped on the surface nearest to the inlet valve seat.
 6. A claim as claimed in claim 1 where the throttle is shaped to partly fill the volume between the inlet valve seat and the throttle seat to reduce this volume to less than 5% of the cylinder swept volume when the throttle is in the nearly closed position for minimum power.
 7. A claim as claimed in claim 1 where the small volume between the inlet valve seat and the throttle quickly fills with inlet air so that when this inlet valve opens the pressure upstream of the inlet valve seat is close to atmospheric.
 8. A claim as claimed in claim 1 where the cam follower is concave at the surface where it contacts the camshaft and where the cam form is concave at the point where the inlet valve starts to open or ends closing.
 9. A claim as claimed in claim 1 where the inlet cam open period corresponds with approximately 60 degrees of camshaft rotation.
 10. A claim as claimed in claim 1 where there are two inlet ports leading to a cylinder and where only one port has a throttle.
 11. A claim as claimed in claim 1 where a fuel injector is located in the small volume between the throttle and the inlet valve seat, so that the heat from the engine helps vaporise fuel without heating a large mass of intake air.
 12. A claim as claimed in claim 1 where the throttle is moved directly by an accelerator pedal or indirectly via a servo and microprocessor or computer influenced by oil, water and air temperature or pressure and driver preferences.
 13. An engine generally as described and as shown in the drawing 1/1. 